Short for polymethylmethacrylate, or more correctly Poly(methyl methacrylate), PMMA is a clear plastic acrylic material that can be used as a replacement for glass. PMMA is commonly used in places where shatter-proof glass or windows are required, such as the puck barriers found in hockey rinks. PMMA is also used in signs, lenses, paints and it is also the core material used in plastic optical fiber.